1. Field of the Invention
This invention relates generally to scanning force microscopes, and more particularly concerns a scanning force microscope with an improved optical lever arm and integrated optics for viewing the lever arm and a sample.
2. Description of Related Art
Scanning force microscopes, also known as atomic force microscopes, are useful for imaging objects as small as atoms. The scanning force microscope is closely related to the scanning tunneling microscope and the technique of stylus profilometry, however in a typical scanning force microscope, deflection of a laser beam by a vertical movement of a probe following the contours of a specimen is amplified by a reflective lever arm to which the probe is mounted. The deflection of the laser beam is typically monitored by a photodetector in the optical path of the deflected laser beam, and the sample is mounted on a stage moveable in minute distances in three dimensions so that the sample can be raster scanned while the vertical positioning of the probe relative to the surface of the sample is maintained substantially constant by a feedback loop with the photodetector controlling the vertical positioning of the sample.
As the sensitivity of the optical lever arm and probe are crucial to the useful operation of such scanning force microscopes, conventional scanning force microscopes generally include optical lever arms of such small dimensions that the optical lever arms and probe assembly can easily be damaged by contact with a sample or during handling, and the optical lever arms and probe assembly is further difficult to handle and mount in the instrument. It would therefore be desirable to provide an improved mount for the probe, which would be easier to handle and position in the instrument.
While a probe can be damaged by too abrupt an approach to a sample before the probe is close enough to the sample to initiate feedback position control, the user typically can not easily view the approach of the lever arm and probe assembly to the surface of the sample to insure precise positioning of the probe. Even where an optical microscope is used in conjunction with the scanning force microscope to view the sample, the arrangement of the optical microscope with the scanning force microscope can be inconvenient and clumsy, and can interfere with the operation of the scanning force microscope. It would therefore also be desirable to provide a scanning force microscope with optics integrated into the scanning force microscope for viewing the optical lever arm and probe, particularly as the probe and sample come in contact.
It would also be desirable to provide a scanning force microscope with the capability of scanning a sample in contact with a fluid, as such a fluid environment can significantly change scanning conditions and opportunities, and can improve the quality of the image of the sample acquired by the instrument. The present invention meets these needs.